Progress 10/01/07 to 09/30/08

Outputs
OUTPUTS: The following reflects major accomplishments for the life of this problem. The Aspen FACE Experiment, the world's largest climate change experiment, was established in 1996 at the Harshaw Forestry Research Farm in conjunction with several other organizations and has continued to present. Funding also supported research on ecosystem-atmosphere exchange of carbon dioxide and water for northern forest ecosystems within the multi-organizational ChEAS and Ameriflux projects. Data were collected to examine the effects of elevated carbon dioxide and ozone on model northern hardwood forest ecosystems (aspen, aspen-paper birch, aspen-sugar maple). Results to date indicate a stimulatory effect of elevated carbon dioxide on growth and a reduction of growth due to elevated ozone which approximately cancels the CO2 effect. Papers were published on the effects of elevated carbon dioxide and ozone on the intra- and inter-specific competitive ability of aspen, and on the effect of elevated temperature and carbon dioxide on the phenolic biochemistry of boreal trees affecting the balance between populations of trees and herbivorous (foliage-consuming) insects. Our research has also shown that climate mediates the effects of carbon dioxide and ozone, an important finding for scientists studying carbon sequestration and global warming. We have also determined that elevated carbon dioxide and ozone affect the wood properties of aspen and birch. Aspen FACE has been highly successful, with over 100 scientists from 20 organizations and 8 countries doing research at the Experiment, and publishing over 170 scientific papers. In open top chamber experiments we found differences in growth among Populus clones in their positive response to CO2 and negative response to ozone. We also studied the biogenic emissions of volatile organic compounds (VOCs) from northern forest trees and found major species and within-species genetic differences in the VOC emission rates. The results indicate that northern forests are large sources of VOCs at the landscape scale which is of interest to air quality regulators. PARTICIPANTS: Neil Nelson Jud Isebrands Richard Dickson Nicanor Saliendra Mark Kubiske Evan McDonald TARGET AUDIENCES: NFS forest managers Federal air quality regulators (EPA) Forest products industry Other researchers Policy makers State forest managers PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
The findings indicate that changes in the global atmosphere likely this century will shift the relative abundance of important tree species in the northern hardwood forest. Higher ozone will increase mortality of aspen, but genetic variation within that species will affect the magnitude of the changes. The three primary species under study in the Aspen FACE Experiment are some of the most prevalent and economically important trees in the northern U.S. The results may have a significant impact on forest management and utilization in the region. In addition there has already been major technology transfer from Aspen FACE to the regulatory sector. In 2008 the U.S. EPA reduced the nationwide secondary standard for ozone exposure (pollution) from 80 ppb to 75 ppb. Five of the fifteen vegetation research papers cited in the decision were from the Aspen FACE Experiment. In the text of the standards revision in the Federal Register the EPA specifically mentioned data from the Aspen FACE project as a significant basis for their decision. This regulatory change is expected to have substantial positive effects on the health, growth, and yield of agricultural crops and forests.

Publications

• Cook, Bruce D.; Bolstad, Paul V.; Martin, Jonathan G.; Heinsch, Faith Ann; Davis, Kenneth J.; Wang, Weiguo; Desai, Ankur R.; Teclaw, Ron M. 2007. Using light-use and production efficiency models to predict photosynthesis and net carbon exchange during forest canopy disturbance. Ecosystems. 11:26-44. (refereed)
• Lilleskov, E.A.; Mattson, W.J.; Storer, A.J. 2008. Divergent biogeography of native and introduced soil macroinvertebrates in North America north of Mexico. Diversity and Distributions: DOI: 10.1111/j. 1472-4642.2008.00487.x
• Svejcar, Tony; Angell, Raymond; Bradford, James A.; Dugas, William; Emmerich, William; Frank, Albert B.; Gilmanov, Tagir; Haferkamp, Marshall; Johnson, Douglas A.; Mayeux, Herman; Mielnick, Pat; Morgan, Jack; Saliendra, Nicanor Z.; Schuman, Gerald E.; Sims, Phillip L.; Snyder, Kereith. 2008. Carbon fluxes on North American rangelands. Rangeland Ecol Manage. 61:465-474. (refereed)
• Uddling, Johan; Teclaw, Ronald M.; Kubiske, Mark E.; Pregitzer, Kurt S.; Ellsworth, David S. 2008. Sap flux in pure aspen and mixed aspen-birch forests exposed to elevated concentrations of carbon dioxide and ozone. Tree Physiology. 28: 1231-1243. (refereed)
• Wolf, Adam; Saliendra, Nick; Akshalov, Kanat; Johnson, Douglas A.; Laca, Emilio. 2008. Effects of different eddy covariance corrections schemes on energy balance closure and comparisons with the modified Bowen ratio system. Agricultural and Forest Meteorology. 148: 942-952. (refereed)

Progress 10/01/06 to 09/30/07

Outputs
Funding supported work on the multi-organizational Aspen FACE (Free-Air Carbon Dioxide and Ozone Enrichment) Experiment, the world's largest atmospheric change experiment. Funding also supported research on ecosystem-atmosphere exchange of carbon dioxide and water for northern forest ecosystems within the multi-organizational ChEAS and Ameriflux projects. Data were collected to examine the effects of elevated carbon dioxide and ozone on model northern hardwood forest ecosystems. A paper was published in Plant Biology on the effects of elevated carbon dioxide and ozone on the intra- and inter-specific competitive ability of aspen. Another paper was published in the Journal of Chemical Ecology on the effect of elevated temperature and CO2 on the phenolic phytochemistry of boreal trees, a key ecological factor determining the balance between populations of plants and herbivorous (foliage-consuming) insects.

Impacts
The findings indicate that changes in the global atmosphere likely this century will shift the relative abundance of important tree species in the northern hardwood forest, and that genetic variation within aspen will affect the magnitude of the changes. The primary species under study (trembling aspen, paper birch, sugar maple)

Publications

• Strong, T.F., Hubbell, A.E., Wiese, A.H., and Erdmann, G.G. 2006. Effects of crown release on growth and quality of even-aged red maple stands. Northern Journal of Applied Forestry 23:229-233. REFEREED #6
• Zalesny, J.A., Zalesny, R.S. Jr., Coyle, D.R., and Hall, R.B. 2007. Growth and biomass of Populus irrigated with landfill leachate. Forest Ecology and Management 248:143-152. REFEREED #4,6
• Zalesny, R.S. Jr., and Bauer, E.O. 2007. Evaluation of Populus and Salix continuously irrigated with landfill leachate I. Genotype-specific elemental phytoremediation. International Journal of Phytoremediation 9:281-306. REFEREED #4,6
• Zalesny, R.S. Jr., and Bauer, E.O. 2007. Evaluation of Populus and Salix continuously irrigated with landfill leachate II. Soils and early tree development. International Journal of Phytoremediation 9:307-323. REFEREED #4,6
• Darbah, Joseph N.T.; Kubiske, Mark E.; Nelson, Neil; Oksanen, Elina; Vaapavuori, Elina; Karnosky, David F. 2007. Impacts of elevated atmospheric CO2 and O3 on paper birch (Betula papyrifera): reproductive fitness. The Scientific World Journal. 7(S1): 240-246. REFEREED #6
• Friend, A.L., Lilleskov, E.A., Zalesny, R.S. Jr., Michaels, R., and McDonald, D.W. 2007. Belowground management of trees: novel perspectives on imaging. HortScience 42(4):799. NONREFEREED #4,6
• Karnosky, D.F.; Werner, H.; Holopainen, T.; et al. 2007. Free-air exposure systems to scale up ozone research to mature trees. Plant Biology. 9: 181-190. REFEREED
• Kubiske, M.E.; Quinn, V.S.; Marquardt, P.E.; Karnosky, D.F. 2006. Effects of elevated atmospheric CO2 and/or O3 on intra- and interspecific competitive ability of aspen. Plant Biology. 9: 342-355. REFEREED #4,6
• Stephens, Britton B.; Bakwin, Peter S.; Tans, Pieter P.; Teclaw, Ron M.; Baumann, Daniel D. 2007. Application of a differential fuel-cell analyzer for measuring atmospheric oxygen variations. Journal of Atmospheric and Oceanic Technology. 24: 82-94. REFEREED #4,6
• Zalesny, J.A., Zalesny, R.S. Jr., Wiese, A.H., Hall, R.B., and Sexton, B. 2006. Phytoremediation of landfill leachate using Populus. In: Seventh Biennial Conference of the Short Rotation Woody Crops Operations Working Group: Short rotation woody crop production systems for wood products, bioenergy and environmental services; September 25-28, 2006; Pasco, WA. p 52. NONREFEREED
• Zalesny, J.A., Zalesny, R.S. Jr., Wiese, A.H., and Hall, R.B. 2006. Using Phyto-recurrent selection to choose Populus genotypes for phytoremediation of landfill leachate. In: Seventh Biennial Conference of the Short Rotation Woody Crops Operations Working Group: Short rotation woody crop production systems for wood products, bioenergy and environmental services; September 25-28, 2006; Pasco, WA. p 51. NONREFEREED #4,6
• Zalesny, R.S. Jr., and Bauer, E.O. 2006. Phyto-recurrent selection: a tree improvement strategy for selecting genotypes used in phytoremediation. In: Seventh Biennial Conference of the Short Rotation Woody Crops Operations Working Group: Short rotation woody crop production systems for wood products, bioenergy and environmental services; September 25-28, 2006; Pasco, WA. p 54. NONREFEREED #4,6
• Zalesny, R.S. Jr., and Wiese, A.H. 2006. Date of shoot collection, genotype, and original shoot position affect early rooting of dormant hardwood cuttings of Populus. Silvae Genetica 55:169-182. REFEREED #4,6
• Zalesny, R.S. Jr. 2006. Genetic and environmental factors affecting early rooting of six Populus genomic groups: implications for tree improvement. In: Seventh Biennial Conference of the Short Rotation Woody Crops Operations Working Group: Short rotation woody crop production systems for wood products, bioenergy and environmental services; September 25-28, 2006; Pasco, WA. p 53. NONREFEREED #4,6

Progress 10/01/05 to 09/30/06

Outputs
Funding supported work on the Aspen FACE (Free-Air Carbon Dioxide and Ozone Enrichment) project initiated in 1997: the world's largest atmospheric change experiment. Data were collected to examine the effects of elevated carbon dioxide and ozone on model northern hardwood forest ecosystems. A paper was published in New Phytologist on the reduction of growth in northern hardwood stands due to ozone pollution. Other papers were published in Global Change Biology describing interactive responses of northern hardwoods to carbon dioxide, ozone, and climate, and in Proceedings of the National Academy of Sciences on the similar responses to elevated carbon dioxide across a broad range of temperate forest species. Another full growing season of data was collected from two mobile eddy flux towers to describe carbon dioxide exchange in regenerating aspen forests and peat bogs in the northern great lakes region. Progress was made on a modeling project to determine possible effects of elevated ozone pollution on forest composition in the next 100 years. We have continued to monitor the incidence of insect activity in all of the aspen and birch FACE trees, and their impact on tree mortality and disease incidence. Ozone treatments interacting with drought are triggering a significant rise in wood boring insects on birch, and an accompanying sharp spike in birch mortality. Carbon dioxide and ozone treatments have had diverse effects (some positive and some negative) on insect populations, and a manuscript describing the results is in process.

Impacts
Impact: Data from this project on ozone effects has been incorporated in the Ozone Criteria Document from which the EPA Ozone Standard is determined. Knowledge of these and other effects elucidated through the project will be useful in monitoring forest health, establishing regulatory policy, developing and modifying forest management practices and plans on both public and private lands, and improving tree selection programs.

Publications

• Mattson, W.J.; Julkunen-Tiitto, R.; Herms, D.A. 2005. CO2 enrichment and carbon partitioning to phenolics: do plant responses accord better with protein competition or the growth-differentiation balance models? OIKOS. 111: 337-347.
• Norby, Richard J.; DeLucia, Evan H.; Gielen, Birgit; Calfapietra, Carlo; Giardina, Christian P.; King, John S.; Ledford, Joanne; et al. 2005. Forest response to elevated CO2 is conserved across a broad range of productivity. PNAS 13 December 2005. 102(50): 18052-18056.
• Pregitzer, Kurt; Loya, Wendy; Kubiske, Mark; Zak, Donald. 2006. Soil respiration in northern forests exposed to elevated atmospheric carbon dioxide and ozone. Oecologia. DOI 10.1007/s00442-006-0381-8.
• Saliendra, Nicanor Z.; Kubiske, Mark E.; Heinsch, Faith Ann; Gustafson, Eric J.; Sturtevant, Brian R.; Heilman, Warren E. 2005. Modeling and scaling up the impacts of ozone on forest productivity in northern Wisconsin. The Ecological Society of America 90th annual meeting; 2005 August 8-12; Montreal, Quebec, Canada. [City, State: Publisher unknown]: 561. Abstract.
• King, John S.; Kubiske, Mark E.; Pregitzer, Kurt S.; Hendrey, George R.; McDonald, Evan P.; Giardina, Christian P.; Quinn, Vanessa S.; Karnosky, David F. 2005. Tropospheric O3 compromises net primary production in young stands of trembling aspen, paper birch and sugar maple in response to elevated atmospheric CO2. New Phytologist. 168: 623-635.
• Kubiske, Mark E.; Quinn, Vanessa S.; Heilman, Warren E.; McDonald, Evan P.; Marquardt, Paula E.; Teclaw, Ron M.; Friend, Alexander L.; Karnosky, David R. 2006. Interannual climatic variation mediates elevated CO2 and O3 effects on forest growth. Global Change Biology. 12: 1054-1068.
• Kubiske, M.E.; Quinn, V.S.; Heilman, W.E.; McDonald, E.P.; Marquardt, P.E.; Teclaw, R.M.; Friend, A.L.; Karnosky, D.F.; Percy, K.E.; Mattson, W.J.; Nelson, N.D. 2005. Feedbacks between climate and the atmosphere in determining forest growth: climatic variation mediates CO2 and O3 effects. In: 7th International carbon dioxide conference; 2005 September 25-30; Boulder, CO. Boulder, CO: Committee of the Seventh International Carbon Dioxide Conference: 739-740.
• Heilman, W.E.; Teclaw, R.M. 2005. Forest micrometeorological responses to increased CO2 and O3 concentrations. In: 7th International carbon dioxide conference extended abstracts; 2005 September 25-30; Boulder, CO. Boulder, CO: Committee of the Seventh International Carbon Dioxide Conference: 731-732.
• Karnosky, D.F.; Pregitzer, K.S.; Zak, D.R.; Kubiske, M.E.; Hendrey, G.R.; Weinstein, D.; Nosal, M.; Percy, K.E. 2005. Scaling ozone responses of forest trees to the ecosystem level in a changing climate. Plant, Cell and Environment. 28: 965-981.

Progress 10/01/04 to 09/30/05

Outputs
Funding supported work on the Aspen FACE (Free-Air Carbon Dioxide and Ozone Enrichment) project initiated in 1997: the largest air pollution experiment in the world. Data were collected to examine the effects of elevated carbon dioxide and ozone on model northern hardwood forest ecosystems. A synthesis paper was published in Plant, Cell and Environment on scaling ozone responses of forest trees to the ecosystem level in a changing climate. Another paper was published on the effect of elevated carbon dioxide on net primary productivity in northern hardwood stands. A manuscript was submitted to Global Change Biology describing interactive responses to carbon dioxide, ozone, and climate. A full growing season of data was collected from two mobile eddy flux towers to describe carbon dioxide exchange in regenerating aspen forests and peat bogs in the northern great lakes region. Progress was made on a modeling project to determine possible effects of elevated ozone pollution on forest composition in the next 100 years. We have monitored the incidence of insect activity in all of the aspen and birch FACE trees, and their impact on tree mortality and disease incidence. Ozone treatments interacting with drought are triggering a significant rise in wood boring insects on birch, and an accompanying sharp spike in birch mortality. This data is being analyzed and prepared for a manuscript and was presented at the Seventh International Carbon Dioxide Conference. Carbon dioxide and ozone treatments have had diverse effects (some positive and some negative) on insect populations, and these studies are being prepared for a manuscript as well.

Impacts
Data from this project on ozone effects has been incorporated in the Ozone Criteria Document from which the EPA Ozone Standard is determined. Knowledge of these and other effects elucidated through the project will be useful in monitoring forest health, establishing regulatory policy, developing and modifying forest management practices and plans on both public and private lands, and improving tree selection programs.

Publications

• Ellsworth, David S.; Reich, Peter B.; Naumburg, Elke S.; et al. 2004. Photosynthesis, carboxylation and leaf nitrogen responses of 16 species to elevated pCO2, across four free-air CO2, enrichment experiments in forest, grassland and desert. Global Change Biology. 10: 1-18.
• Giardina, Christian; Kubiske, Mark; McDonald, Evan; et al. [2004]. Effects of elevated CO2, and O3, on leaf area index in mixed aspen and birch stands. In: Abstracts: the Ecological Society of America, 89th annual meeting: lessons of Lewis & Clark ecological exploration of inhabited landscapes; 2004 August 1-6; Portland, OR. [Portland, OR: The Ecological Society of America]: 177-178. Abstract.
• Kubiske, Mark E.; McDonald, Evan; Quinn, Vanessa; et al. [2004]. Growth dynamics of tree communities exposed to elevated atmospheric CO2, and O3, for six years. In: Abstracts: the Ecological Society of America, 89th annual meeting: lessons of Lewis & Clark ecological exploration of inhabited landscapes; 2004 August 1-6; Portland, OR. [Portland, OR: The Ecological Society of America]: 283. Abstract.
• Mattson, William J.; Kuokkanen, Kari; Niemela, Pekka; et al. 2004. Elevated CO21 alters birch resistance to Lagomorpha herbivores. Global Change Biology. 10: 1402-1413.
• Rishi, A. S.; Nelson, Neil D.; Munir, S.; et al. [2004]. Comparative analysis of gene expression induced by safeners and abiotic stresses in Populus. In: 12th new phytologist symposium: functional genomics of environmental adaptation in Populus: program & abstracts; 2004 October 10-13; Gatlinburg, TN. [Gatlinburg, TN: New Phytoloogist]: 44. Abstract P56.

Progress 10/01/03 to 09/30/04

Outputs
Funding supported work on the aspen FACE experiment: the largest air pollution experiment in the world. Data were collected to examine the effects of elevated carbon dioxide and ozone on model forest ecosystems. A manuscript was published comparing photosynthetic properties across several elevated CO2 experiments. A manuscript was submitted to Nature describing net primary productivity, and another manuscript is in preparation for Science describing interactive responses to CO2, ozone, and climate. Work was initiated on two mobile eddy flux towers to describe CO2 exchange in regenerating aspen forests and peat bogs in the northern great lakes region. A modeling project was initiated to determine possible effects of elevated ozone pollution on forest composition in the next 100 years. We have monitored the incidence of insect activity in all of the aspen and birch FACE trees, and their impact on tree mortality and disease incidence. Ozone treatments are triggering a significant rise in wood boring insects on birch, and an accompanying sharp spike in birch mortality. This data is being analyzed and prepared for a manuscript. Six years of CO2 treatments have had diverse effects (some positive and some negative) on insect populations, and these studies are being prepared for a manuscript as well.

Impacts
These data suggest that rising tropospheric ozone levels will induce widespread susceptibility of birches to wood boring beetles, and heightened birch mortality. Knowledge of these and other effects elucidated through the project will be useful in monitoring forest health, establishing regulatory policy, developing and modifying forest management practices and plans on both public and private lands, and improving tree selection programs.

Publications

• Giardina, C.; McDonald, E.; Kubiske, M.; et al. 2004. The effects of elevated CO2 and 03 on litterfall in mixed aspen and birch stands at the Rhinelander FACE facility. In: Managing forest resources in the 21st century: an integrated approach, the North American forest biology workshop (abstracts); 2004 July 12-15; Houghton, MI. [Houghton, MI: Michigan Technological University]: 70. Abstract.

Progress 10/01/02 to 09/30/03

Outputs
Funding supported the aspen FACE experiment; the largest open-air air pollution experiment in the world. Data were collected to determine the effects of elevated concentrations of atmospheric CO2 and O3 on the relative biomass distribution of three tree species, their growth characteristics, and their competitive interactions. Two manuscripts are in preparation. Work is continuing to determine whole-canopy photosynthesis, nitrogen use efficiency and water use under elevated CO2 and O3. We are working with several collaborators to compute an ecosystem carbon budget for three forest types under global change conditions. Work is on-going to determine the impact of insect feeding on photosynthetic performance under elevated CO2 and O3. The ecological impacts of forest tent caterpillar on trees exposed to elevated CO2 and O3 is underway. A population genetics study is underway to determine migration routes of spruce budworm and the effects of forest fragmentation.

Impacts
Knowledge of these effects will be useful in establishing administrative and regulatory policy, monitoring forest health, and improving tree selection programs. Understanding the responses of trees and forests to CO2 and O3 will provide the basis for development of new management practices in forests and nurseries.

Publications

• Hews, Diana K.; Quinn, Vanessa S. 2003. Endocrinology of species differences in sexually dichromatic signals. In: Fox, Stanley F.; McCoy, J. Kelly; Baird, Troy A., eds. Lizard social behavior. Baltimore, MD: The Johns Hopkins University Press: 253-277.
• Karnosky, D.F.; Zak, D.R.; Pregitzer, K.S.; et al. 2003. Tropospheric O3 moderates responses of temperate hardwood forests to elevated CO2: a synthesis of molecular to ecosystem results from the Aspen FACE project. Functional Ecology. 17: 289-304.
• Kubiske, Mark E.; McDonald, Evan P. 2002. Photosynthetic carbon isotope discrimination in tree canopies under CO2 and O3 enrichment. In: The Ecological Society of America 87th annual meeting: Society for Ecological Restoration 14th international conference abstracts; 2002 August 4-9; Tucson, AZ. Washington DC: The Ecological Society of America: 375-376. Abstract.
• McDonald, E.P.; Kruger, E.L.; Riemenschneider, D.E.; Isebrands, J.G. 2002. Competitive status influences tree-growth responses to elevated CO2 and O3 in aggrading aspen stands. Functional Ecology. 16: 792-801.
• McDonald, Evan P.; Kruger, Eric L.; Isebrands, Jud G. 2002. Competition and growth in aggrading aspen stands exposed to elevated CO2 and tropospheric ozone. In: The Ecological Society of America 87th annual meeting: Society for Ecological Restoration 14th international conference abstracts; 2002 August 4-9; Tucson, AZ. Washington, DC: The Ecological Society of America: 207. Abstract.
• Percy, Kevin E.; Awmack, Caroline S.; Lindroth, Richard L.; et al. 2003. Altered performance of forest pests under atmospheres enriched by CO2 and O3. Nature. 420: 403-407.
• McDonald, E.P.; Kruger, E.L.; Riemenschneider, D.E.; Isebrands, J.G. 2002. Competitive status influences tree-growth responses to elevated CO2 and O3 in aggrading aspen stands. Functional Ecology. 16: 792-801.

Progress 10/01/01 to 09/30/02

Outputs
A new initiative was launched for understanding CO2 and O3 effects on canopy-level processes of northern forests. Various lines of research were published showing effects of these gasses on: 1) competition among species and genotypes, 2) efficiency of nitrogen use in a forest canopy, 3) growth and functioning of roots and root systems, 4) simulating growth responses and measured growth responses. Effects of these gasses on the production of secondary metabolites was initiated linking tree defenses to damage by leaf feeding and wood boring insects. This work was accomplished at the aspen FACE experiment, the largest field-based global change experiment in the world. Renewed funding from the Department of Energy Office of Biological and Environmental Research was received for another three years. Work also continued in monitoring CO2 and water vapor fluxes from a network of four eddy covariance towers located throughout northern Wisconsin. A manuscript is in preparation.

Impacts
(N/A)

Publications

• Lindroth, Richard L.; Kopper, Brian J.; Parsons, William F.J.; Bockheim, James G.; Karnosky, David F.; et al. 2001. Consequences of elevated carbon dioxide and ozone for foliar chemical composition and dynamics in trembling aspen (Populus tremuloides) and paper birch (Betula papyrifera). Environmental Pollution. 115: 395-404.
• Takeuchi, Y.; Kubiske, M.E.; Isebrands, J.G.; Pregitzer, K.S.; Hendrey, G.; Karnosky, D.F. 2001. Photosynthesis, light and nitrogen relationships in a young deciduous forest canopy under open-air CO2 enrichment. Plant, Cell and Environment. 24: 1257-1268.
• Kubiske, M.E.; Godbold, D.L. 2001. Influence of CO2 on the growth and function of roots and root systems. In: Karnosky, David F.; Ceulemans, Reinhart; Scarascia-Mugnozza, Giuseppe E.; Innes, John L., eds. The impact of carbon dioxide and other greenhouse gases on forest ecosystems: report no. 3 of the IUFRO task force on environmental change. IUFRO Res. Ser. 8. Wallingford, Oxon, UK: CABI Publishing, CAB International: 147-191.
• Martin, M.J.; Host, G.E.; Lenz, K.E.; Isebrands, J.G. 2001. Simulating the growth response of aspen to elevated ozone: a mechanistic approach to scaling a leaf-level model of ozone effects on photosynthesis to a complex canopy architecture. Environmental Pollution. 115: 425-436.
• McDonald, Evan P.; Kruger, Eric L.; Isebrands, Jud G. 2001. Light and nitrogen use efficiencies for temperate hardwood stands exposed to elevated CO2 and O3. In: Ecological Society of America 86th annual meeting abstracts; 2001 August 5-10;
• Wustman, B.A.; Oksanen, E.; Karnosky, D.F.; Noormets, A.; Isebrands, J.G.; et al. 2001. Effects of elevated CO2 and O3 on aspen clones varying in O3 sensitivity: can CO2 ameliorate the harmful effects of O3? Environmental Pollution. 115: 473-481.
• Dickson, Richard E.; Coleman, M.D.; Pechter, Priit; Karnosky, David. 2001. Growth and crown architecture of two aspen genotypes exposed to interacting ozone and carbon dioxide. Environmental Pollution. 115: 319-334.
• Gandhi, K.J.; Anderson, P.; Gilmore, D.W.; Haack, R.A.; Mattson, W.J.; Zasada, J.C.; Seybold, S.J. 2002. Sub-boreal beetles in wind-disturbed and prescribed-burned forests. 1 p. Poster.
• Isebrands, J.G.; McDonald, E.P.; Kruger, E.; Hendrey, G.; Percy, K.; et al. 2001. Growth responses of Populus tremuloides clones to interacting elevated carbon dioxide and tropospheric ozone. Environmental Pollution. 115: 359-371.
• King, J.S.; Pregitzer, K.S.; Zak, D.R.; Kubiske, M.E.; Holmes, W.E. 2001. Correlation of foliage and litter chemistry of sugar maple, Acer saccharum, as affected by elevated CO2 and varying N availability, and effects on decomposition. Oikos. 94(3): 403-416
• Kubiske, Mark E.; Zak, Donald R.; Pregitzer, Kurt S.; Takeuchi, Yu. 2002. Photosynthetic acclimation of overstory Populus tremuloides and understory Acer saccharum to elevated atmospheric CO2 concentration: interactions with shade and soil nitrogen. Tree Physiology. 22: 321-329.
• Isebrands, J.; McDonald, E.; Karnosky, D. 2001. Consequences of interacting elevated CO2 and tropospheric ozone on cumulative growth and nitrogen dynamics in a trembling aspen (Populus tremuloides) stand. In: Abstracts: Challenges of a changing earth; global change open science conference; 2001 July 10-13; Amsterdam, The Netherlands. Amsterdam, The Netherlands: CONGREX HOLLAND BV: 137. Abstract. P.1.14.03.
• Karnosky, D.F.; Oksanen, E.; Dickson, R.E.; Isebrands, J.G. 2001. Impacts of interacting greenhouse gases on forest ecosystems. In: Karnosky, David F.; Ceulemans, Reinhart; Scarascia-Mugnozza, Giuseppe E.; Innes, John L., eds. The impact of carbon dioxide and other greenhouse gases on forest ecosystems: report no. 3 of the IUFRO task force on environmental change. IUFRO Res. Ser. 8. Wallingford, Oxon, UK: CABI Publishing, CAB International: 253-267.
• Kruger, Eric L.; McDonald, Evan P.; Erickson, John E. 2001. Does a decrease in transpiration mediate N deprivation in trees exposed to elevated CO2? In: Ecological Society of America 86th annual meeting abstracts; 2001 August 5-10; Madison, WI. Washington, DC: The Ecological Society of America: 305. Abstract.
• Host, G.E.; Theseira, G.W.; Heim, C.S.; Isebrands, J.G.; Graham, R.L. 1999. EPIC-ECOPHYS: a linkage of empirical and process models for simulating poplar plantation growth. In: Amaro, Ana; Tome, Margarida, eds. Empirical and process based models for forest tree and stand growth simulation; 1997 September 21-27; Oeiras, Portugal. [Portugal]: Publicidade e Servicos, Lda.: 419-429.